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.TH POLL.H 3HEAD "Sep 9, 2004"
.SH NAME
poll.h, poll \- definitions for the \fBpoll()\fR function
.SH SYNOPSIS
.LP
.nf
#include <\fBpoll.h\fR>
.fi

.SH DESCRIPTION
.sp
.LP
The <\fBpoll.h\fR> header defines the \fBpollfd\fR structure, which includes
the following members:
.sp
.ne 2
.na
\fB\fBint fd\fR\fR
.ad
.RS 17n
the following descriptor being polled
.RE

.sp
.ne 2
.na
\fB\fBshort events\fR\fR
.ad
.RS 17n
the input event flags (see below)
.RE

.sp
.ne 2
.na
\fB\fBshort revents\fR\fR
.ad
.RS 17n
the output event flags (see below)
.RE

.sp
.LP
The <\fBpoll.h\fR> header defines the following type through \fBtypedef\fR:
.sp
.ne 2
.na
\fB\fBnfds_t\fR\fR
.ad
.RS 10n
an unsigned integer type used for the number of file descriptors
.RE

.sp
.LP
The implementation supports one or more programming environments in which the
width of \fBnfds_t\fR is no greater than the width of type long. The names of
these programming environments can be obtained using the \fBconfstr()\fR
function or the \fBgetconf\fR utility. See \fBconfstr\fR(3C) and
\fBgetconf\fR(1).
.sp
.LP
The following symbolic constants are defined, zero or more of which can be
OR'ed together to form the \fBevents\fR or \fBrevents\fR members  in the
\fBpollfd\fR structure:
.sp
.ne 2
.na
\fB\fBPOLLIN\fR\fR
.ad
.RS 14n
Data other than high-priority data can be read without blocking.
.RE

.sp
.ne 2
.na
\fB\fBPOLLRDNORM\fR\fR
.ad
.RS 14n
Normal data can be read without blocking.
.RE

.sp
.ne 2
.na
\fB\fBPOLLRDBAND\fR\fR
.ad
.RS 14n
Priority data can be read without blocking.
.RE

.sp
.ne 2
.na
\fB\fBPOLLPRI\fR\fR
.ad
.RS 14n
High priority data can be read without blocking.
.RE

.sp
.ne 2
.na
\fB\fBPOLLOUT\fR\fR
.ad
.RS 14n
Normal data can be written without blocking.
.RE

.sp
.ne 2
.na
\fB\fBPOLLWRNORM\fR\fR
.ad
.RS 14n
Equivalent to \fBPOLLOUT\fR.
.RE

.sp
.ne 2
.na
\fB\fBPOLLWRBAND\fR\fR
.ad
.RS 14n
Priority data can be written.
.RE

.sp
.ne 2
.na
\fB\fBPOLLERR\fR\fR
.ad
.RS 14n
An error has occurred (\fBrevents\fR only).
.RE

.sp
.ne 2
.na
\fB\fBPOLLHUP\fR\fR
.ad
.RS 14n
Device has been disconnected (\fBrevents\fR only).
.RE

.sp
.ne 2
.na
\fB\fBPOLLNVAL\fR\fR
.ad
.RS 14n
Invalid \fBfd\fR member (\fBrevents\fR only).
.RE

.sp
.LP
The significance and semantics of normal, priority, and high-priority data are
file and device-specific.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR getconf (1),
.BR poll (2),
.BR confstr (3C),
.BR attributes (7),
.BR standards (7)
